Clamping device

ABSTRACT

A clamping device has a clamp arm pivotally housed inside a body, and a locating section for positioning workpieces is provided on an upper portion of the body. The locating section is formed with a slit hole which enables a claw portion of the clamp arm to protrude outside, and is provided inside with a shutter facing the slit hole and being movable. The claw portion of the clamp arm is inserted through a clamp hole of the shutter. Then, when the clamp arm moves inside the body in the axial direction and rotates, the shutter moves integrally with the clamp arm in the axial direction to cover the slit hole. Thus, the opening portion of the slit hole is suitably covered except that portion occupied by the claw portion so that foreign matter and the like can be prevented from entering the locating section through the slit hole.

TECHNICAL FIELD

The present invention relates to a clamping device capable of clamping aworkpiece with a clamp arm that is pivotable a predetermined angle undera driving action of a drive section.

BACKGROUND ART

The present applicant has proposed a clamping device for clampingcomponents of, for example, a motor car or the like when the componentsare welded (refer to Japanese Patent No. 3941059).

The clamping device includes a clamp body and a workpiece receivingmember provided on an upper portion of the clamp body, and a hollowlocating pin protruding upward is provided at a center portion of theupper end portion of the workpiece receiving member. A clamp arm ismovably inserted inside the locating pin, and a distal end portion ofthe clamp arm is configured to protrude outside from a clamp hole whichopens on a lateral side of the locating pin.

On the other hand, a lower portion of the clamp body is connected to alinear actuator, and an output member of the linear actuator is insertedinto the clamp body and is connected at its end portion to the clamp armmutually swingably with a connecting pin.

Then, when pressurized fluid is supplied to the linear actuator, theoutput member is moved in the axial direction, whereby the clamp armswings inside the clamp body, the workpiece receiving member, and thelocating pin. As a result, a hook-like end portion formed at an upperend portion of the clamp arm protrudes outside through the clamp hole ofthe locating pin and clamps a workpiece mounted on a seating surface ofthe workpiece receiving member. In this clamping state, welding isperformed.

SUMMARY OF INVENTION

A general object of the present invention is to provide a clampingdevice capable of reliably preventing foreign matter and the like fromentering the inside of a body.

In one aspect, according to the present invention, there is provided aclamping device which comprises a drive section having a displacementbody movable in an axial direction under an action of supplyingpressurized fluid, a body connected to the drive section and having amounting portion on which a workpiece is mounted, a clamp arm connectedto the displacement body and pivotably supported relative to the body, alocating section protruding in the axial direction relative to themounting portion and being inserted into a positioning hole formed inthe workpiece, wherein a linear motion of the displacement bodyoutputted by the drive section is converted into a pivotal motion of theclamp arm, a slit hole is formed in the locating section and opens alongthe axial direction, a claw portion of the clamp arm housed inside thelocating section protrudes through the slit hole, the workpiece isclamped between the mounting portion and the claw portion. In theclamping device, a cover member that faces the slit hole and is movablein the axial direction is provided inside the locating section, and thecover member is provided with an opening into which the claw portion isinserted, the opening faces the slit hole.

According to the present invention, when the workpiece that is mountedon the mounting portion and through which the locating section isinserted is clamped by the clamp arm, the clamp arm is moved in theaxial direction inside the body and the locating section under theaction of the drive section. Thus, because the cover member is movedintegrally with the clamp arm while covering the slit hole, the openingportion of the slit hole is reliably covered. Therefore, even when theclaw portion protrudes outside from the slit hole through the openingand clamps the workpiece, the opening portion of the slit hole exceptthat portion occupied by the claw portion is completely covered by thecover member.

Consequently, foreign matter such as spatters and the like which areproduced in performing, for example, a welding work with the workpiececlamped by the clamp arm can reliably be prevented by the cover memberfrom entering the inside of the locating section and the body.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings, in which apreferred embodiment and modifications of the present invention areshown by way of illustrative examples.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a clamping device in one embodimentaccording to the present invention;

FIG. 2 is a perspective view in a disassembled state of the clampingdevice shown in FIG. 1;

FIG. 3 is a front view of the clamping device shown in FIG. 1;

FIG. 4 is a sectional view taken along line IV-IV in FIG. 3;

FIG. 5 is an entire sectional view of the clamping device shown in FIG.4 in an unclamping state;

FIG. 6 is an enlarged sectional view of a locked state of a clamp armunder a lock switching mechanism shown in FIGS. 4 and 5; and

FIGS. 7A to 7F are perspective views of shutters in first to sixthmodifications according to the present invention.

DESCRIPTION OF EMBODIMENTS

As shown in FIGS. 1 to 5, a clamping device 10 includes a cylindersection 14 having a piston (displacement body) 12 displaced under anaction of supplying pressurized fluid (for example, compressed air), ahollow cylindrical body 16 connected to the cylinder section 14, a clampsection 18 provided swingably inside the body 16 and being capable ofholding workpieces W1, W2 (refer to FIGS. 4 and 5), and a lock switchingmechanism (lock mechanism) 22 provided between the cylinder section 14and the body 16 and being capable of restricting movements of a clamparm 20.

Incidentally, the aforementioned clamping device 10 is used, forexample, to hold, as the workpieces W1, W2, plate materials that areused for automotive panels and in this way is used in a manufacturingline where one workpiece W1 and another workpiece W2 are welded.

The cylinder section 14 includes a cylinder tube 24, a rod cover 26connected to an upper end portion of the cylinder tube 24, the piston 12movably provided inside the cylinder tube 24, and a piston rod(displacement body) 28 connected to the piston 12 and supported movablyrelative to the rod cover 26.

The cylinder tube 24 is formed as, for example, a bottomed cylinderopening at an upper end portion. Inside the cylinder tube 24, a cylinderchamber 30 with a circular cross section is formed extending in theaxial direction (the arrow A-B direction). Outside the cylinder tube 24,a pair of first and second fluid ports 32, 34 is formed into whichpressurized fluid is supplied and from which the pressurized fluid isdischarged.

The first and second fluid ports 32, 34 are connected to a pressurizedfluid supply (not shown) through tubes and switch valves (not shown),are formed a predetermined distance apart from each other in the axialdirection of the cylinder tube 24, and are in communication with thecylinder chamber 30 through communication passages 36.

Incidentally, the first fluid port 32 is provided on a lower side (thearrow A direction) of the body 16, while the second fluid port 34 isprovided on an upper side (the arrow B direction) of the body 16.

The rod cover 26 is formed to have a circular cross section, and a rodhole 38 into which the piston rod 28 is inserted perforates the rodcover 26 at a central portion thereof. A rod packing 40 provided insidethe rod cover 26 slidably contacts an outer peripheral surface of thepiston rod 28. The rod cover 26 is fitted in the cylinder tube 24closing the opening upper end portion of the cylinder tube 24.

The piston 12 has a cylindrical cross section and is provided movablyalong the cylinder chamber 30. The piston rod 28 is inserted into acentral portion of the piston 12 along the axial direction and isconnected to the piston 12. A piston packing 42, a wear ring 44, and amagnet 46 are fitted in annular grooves formed on the outer peripheralsurface of the piston 12.

The piston rod 28 comprises a shaft body having a circular cross sectionand extends a predetermined length toward the body 16 side (the arrow Bdirection) with respect to the piston 12. The piston rod 28 is insertedinto the rod hole 38 of the rod cover 26 and is supported being slidablealong the axial direction (the arrow A-B direction).

Further, an arm holding portion 48 being bifurcated is formed at anupper end portion on the body 16 side of the piston rod 28. The armholding portion 48 is connected to one end portion of the clamp arm 20with a connecting pin 52 which is inserted into a first pin hole 50extending through the arm holding portion 48 in a directionperpendicular to the longitudinal direction.

Incidentally, the piston rod 28 is accommodated extending from thecylinder section 14 to the inside of the body 16 through the lockswitching mechanism 22.

The body 16 is formed of, for example, a metal material and is providedcoaxially with the cylinder section 14 through the lock switchingmechanism 22. The clamp arm 20 is swingably housed inside the body 16,and a locating section 54 is mounted on an upper portion of the body 16with a holder 56 in between.

In the lateral surface of the body 16, mounting holes 58 (refer to FIGS.1 and 2) for fixing the clamping device 10 in the manufacturing line areformed.

The locating section 54 has a cylindrical shape extending in the axialdirection and is provided at its lateral surface with a slit hole 60through which a portion of the clamp arm 20 is able to protrude outside.This slit hole 60 is formed long and straight to have a predeterminedlength along the axial direction (the arrow A-B direction) of thelocating section 54.

Further, the locating section 54 has an annular mounting portion 62which expands radially outward and is provided in the vicinity of anintermediate portion in the axial direction, and this mounting portion62 is planar-shaped substantially perpendicular to the axis of thelocating section 54. Then, as shown in FIGS. 4 and 5, when the locatingsection 54 is inserted into positioning holes h of the workpieces W1,W2, the workpieces W1, W2 are held in a substantially horizontalposition by abutment on the mounting portion 62.

On the other hand, inside the locating section 54, a chamber 64 having acircular cross section is formed extending in the axial direction and isin communication with the outside through the slit hole 60. Also insidethe locating section 54, a cylindrical shutter (cover member) 66 isprovided movably along the axial direction (the arrow A-B direction).

Then, the locating section 54 is fixed with its lower end portion fittedin a holder hole 68 of the holder 56 formed in a plate shape, and theholder 56 is fixed by plural bolts 70 to the body 16 covering an upperend portion of the body 16. Thus, the locating section 54 is provided toprotrude a predetermined height upward (in the arrow B direction) withrespect to the upper end portion of the body 16.

The shutter 66 is cylindrically formed of, for example, a metal materialand is at least longer along the axial direction (the arrow A-Bdirection) than the longitudinal dimension of the slit hole 60 in thelocating section 54 and to be substantially the same as, or slightlysmaller than, an inner peripheral diameter of the locating section 54.

Further, in an outer peripheral surface of the shutter 66, a clamp hole(opening) 72 is formed through the shutter 66 in the radial direction.The clamp hole 72 is formed at a substantially center portion in theaxial direction (the arrow A-B direction) of the shutter 66 and has arectangular cross section which is made up of two sides extending in theaxial direction of the shutter 66 and two sides extending in a directionperpendicular to the axial direction.

Then, the shutter 66 is disposed so that the clamp hole 72 faces theslit hole 60. The other end portion of the clamp arm 20, details ofwhich will be described later, is inserted inside the shutter 66, and aclaw portion 76 of the clamp arm 20, which is also described later, isinserted into the clamp hole 72.

The clamp section 18 has a long clamp arm 20 formed of a metal materialand housed inside the body 16. One end of the clamp arm 20 is insertedinto a space between the bifurcated portions of the arm holding portion48 of the piston rod 28 and is pivotably connected to the arm holdingportion 48 because the connecting pin 52 inserted into the first pinhole 50 of the piston rod 28 is inserted through a second pin hole 74.That is, the clamp arm 20 is pivotable about one (i.e., lower) endportion into which the connecting pin 52 is inserted.

Further, the other end portion side of the clamp arm 20 is housed insidethe shutter 66 and the locating section 54, and the other end portion isprovided with a hook-like claw portion 76 which is bent at right anglerelative to the longitudinal direction of the clamp arm 20. The clawportion 76 is formed to laterally protrude a predetermined lengthrelative to the other end portion of the clamp arm 20, is inserted intothe clamp hole 72 of the shutter 66 and is also inserted into the slithole 60 of the locating section 54.

Furthermore, the clamp arm 20 is provided with a link groove 78 at asubstantially center portion in the longitudinal direction thereof, andthe link groove 78 is constituted by a first groove portion 80 extendingsubstantially in parallel to the longitudinal direction of the clamp arm20 and a second groove portion 82 joined with a lower side (in the arrowA direction) of the first groove portion 80 and bent at a predeterminedangle. As the link groove 78 extends downward, the second groove portion82 slants to gradually come close to a lateral side of the cylindersection 14. On the lateral side, the first and second fluid ports 32, 34open.

Further, a link pin 84 supported by sidewalls of the body 16 is insertedinto the link groove 78 with the clamp arm 20 housed inside the body 16.

The lock switching mechanism 22 has a housing 86, a lock ring (lockmember) 88 housed inside the housing 86, and an end block 90 closing anupper end portion of the housing 86, and a lock release port 92 opens ona side surface of the housing 86. The lock release port 92 is incommunication with the inside of the housing 86.

The housing 86 is formed in a hollow shape and is provided between theupper end portion of the cylinder section 14 and the lower end portionof the body 16 being coupled to both. The lock release port 92 opens inthe same direction as the first and second fluid ports 32, 34, and isconnected to the pressurized fluid supply (not shown) through, forexample, tubes and switch valves (both not shown).

The lock ring 88 is, for example, annular-shaped and is providedtiltably inside the housing 86. The piston rod 28 is inserted into alock hole 94 that extends through the center of the lock ring 88. Thelock hole 94 has a diameter that is slightly larger than the outerdiameter of the piston rod 28.

Further, a plate-like release lever 96 is provided on one end (i.e.,lower end) surface of the lock ring 88. The release lever protrudes inthe radial direction. A distal end of the release lever 96 is insertedinto a working hole 98 that opens on a sidewall of the housing 86.Incidentally, the working hole 98 is covered by a cover 100 which isdetachably attached to the sidewall of the housing 86.

Furthermore, a taper portion 102 constituted by a tapering surface onone end surface of the lock ring 88 is formed and is apart from the endsurface of the rod cover 26. The taper portion 102 can be tiltedslightly towards the rod cover 26 side.

A return spring (resilient member) 104 is provided between the lock ring88 and the rod cover 26 on a side opposite to the taper portion 102. Asshown in FIG. 6, the lock ring 88 is urged and tilted by the resilientforce of the return spring 104 in the same direction as the releaselever 96 separates from the rod cover 26. Thus, tilted by the resilientforce of the return spring 104, the lock ring 88 is brought intoabutment on the piston rod 28 that has been inserted into the lock hole94, whereby the piston rod 28 is put in a lock state where movement isrestricted by the resistance caused by the abutment.

Further, when pressurized fluid is supplied from the lock release port92 into the inside of the housing 86, the lock ring 88 is pressed andtilted in the opposite direction against the resilient force of thereturn spring 104 thereby to be in a horizontal position. As a result,the piston rod 28 is released from the lock state caused by the lockring 88 and brought into a lock released state in which the piston rod28 is movable in the axial direction.

Furthermore, even in the case where it is unable to supply the lockrelease port 92 with pressurized fluid, a worker (not illustrated)detaches the cover 100 and pushes the release lever 96 down toward thecylinder section 14 side (the arrowed A direction) through the workinghole 98, whereby the lock ring 88 is brought into a substantiallyhorizontal position and it becomes possible to manually release the lockstate of the piston rod 28.

The clamping device 10 according the embodiment of the present inventionis basically configured as described hereinabove, and the operation andadvantageous effects of the clamping device 10 will be describedhereunder. Incidentally, the operation will be described on theassumption that an unclamping state shown in FIG. 5 is an initial state.

In this initial state, as shown in FIG. 5, pressurized fluid has beensupplied to the cylinder chamber 30 of the cylinder tube 24 from thefirst fluid port 32, while the second fluid port 34 is in a state ofbeing open to the atmosphere. Therefore, the piston 12 has been movedupward (the arrowed B direction) under the pressing action ofpressurized fluid and is abutting the end surface of the rod cover 26.Further, the clamp arm 20 has been pivoted by the elevation of thepiston rod 28, so that the claw portion 76 has been retracted inside thelocating section 54 of the body 16.

In the aforementioned initial state of the clamping device 10, theworkpieces W1, W2 are transferred by a transfer equipment or the like(not shown), the locating section 54 is inserted into the positioningholes h of the workpieces W1, W2. Thus, one workpiece W1 and the otherworkpiece W2 are mounted such that one is put on the other on the uppersurface of the mounting portion 62 of the body 16 and are held in asubstantially horizontal position.

In this case, as shown in FIG. 5, the claw portion 76 of the clamp arm20 is housed in the locating section 54 and does not protrude outwardsthrough the slit hole 60 and thus is able to avoid the contact with theworkpieces W1, W2, so that the workpieces W1, W2 can be smoothly movedto and placed on the mounting portion 62.

After the confirmation of the placing of the workpieces W1, W2, thepressurized fluid from the pressurized fluid supply is supplied to thesecond fluid port 34 instead of the first fluid port 32 by the switchingaction of the switching valve (not shown). As a result, the piston 12begins to move downward and this causes the clamp arm 20 connected tothe piston rod 28 to become pivotable. By the pressurized fluid suppliedfrom the second fluid port 34, the piston 12 and the piston rod 28 aremoved downward along the axial direction.

Thus, the clamp arm 20 is lowered, whereby the claw portion 76 islowered along the slit hole 60 and further the shutter 66 having theclaw portion 76 inserted into the clamp hole 72 is lowered together. Atthe same time, the link pin 84 begins to be relatively moved from thesecond groove portion 82 of the link groove 78 to the first grooveportion 80. The clamp arm 20 is pivoted counterclockwise about theconnecting pin 52, and together with this pivot movement, the clawportion 76 starts to protrude outside the slit hole 60 through the clamphole 72.

As a result, as shown in FIG. 4, the claw portion 76 of the clamp arm 20sticks out of the locating section 54 and is brought into abutment onthe upper surface of the workpiece W1 mounted together with theworkpiece W2 on the mounting portion 62, pressing the workpiece W1downwards, whereby the workpieces W1, W2 are clamped in a substantiallyhorizontal position between the mounting portion 62 and the clamp arm20.

Further, when the supply of pressurized fluid to the lock release port92 is stopped in this clamping state of the workpieces W1, W2, the lockring 88 is tilted by the resilient force of the return spring 104 asshown in FIG. 6 and is tilted relative to the piston rod 28 to bebrought into contact with the piston rod 28 through the lock hole 94,whereby the pivotal movement of the clamp arm 20 is locked in the statewhere the workpieces W1, W2 are clamped.

That is, even in the case where the supply of the pressurized fluid tothe second fluid port 34 is stopped, the state of clamping theworkpieces W1, W2 with the clamp arm 20 is reliably kept by the lockswitching mechanism 22.

Thereafter, in the clamping state where the workpieces W1, W2 areclamped at a predetermined position by the clamping device 10 asdescribed above, the welding operation of one workpiece W1 and the otherworkpiece W2 is performed by a welding apparatus (not shown). At thistime, as shown in FIGS. 3 and 4, part of the slit hole 60 is covered bythe outer peripheral surface of the shutter 66 provided inside the slithole 60, that part not being a portion occupied by the claw portion 76protruding outside. Accordingly, spatters and the like produced at thetime of welding can be prevented from entering inside through the slithole 60.

Next, description will be given regarding the case that the clampingstate of the workpieces W1, W2 is released (the unclamping state) afterthe completion of the welding operation of the workpieces W1, W2.

In the clamping device 10 shown in FIG. 4, pressurized fluid is suppliedto the lock release port 92 to release the lock state of the clamp arm20, and together with this, pressurized fluid is supplied from the firstfluid port 32 to the cylinder chamber 30. As a result, the piston 12 andthe piston rod 28 move upward (the arrow B direction) and the clamp arm20 moves upward while being pivoted.

Because the link pin 84 moves from the first groove portion 80 to thesecond groove portion 82 of the link groove 78, the clamp arm 20 pivotsclockwise about the connecting pin 52, whereby the claw portion 76 isretracted inside the locating section 54.

At the same time, together with the elevation of the clamp arm 20, theshutter 66 through which the claw portion 76 is inserted is alsoelevated together.

Then, when the piston 12 is moved to a position where the piston 12abuts the rod cover 26 as shown in FIG. 5, the claw portion 76 iscompletely retracted inside the locating section 54 through the slithole 60 while being kept inserted into the clamp hole 72 of the shutter66, whereby the state transitions into the unclamping state where thestate of the workpieces W1, W2 being clamped by the claw portion 76 isreleased. Incidentally, when in this unclamping state, the device isalso in the lock release state where the pressurized fluid iscontinuously supplied to the lock release port 92.

As described above, in the present embodiment, the clamp arm 20 ispivotably housed inside the body 16 that is part of the clamping device10, the locating section 54 provided at the upper end portion of thebody 16 is provided with the shutter 66 which is movable vertically (thearrow A-B direction) together with the clamp arm 20, and the shutter 66formed in the cylindrical shape is provided to face the slit hole 60 ofthe locating section 54 through which the claw portion 76 of the clamparm 20 protrudes outside.

Then, the claw portion 76 of the clamp arm 20 is able to move verticallyalong the slit hole 60 under the drive action of the cylinder section14, and the shutter 66 movable together with the claw portion 76 is ableto reliably close the opening portion of the slit hole 60 except thearea occupied by the claw portion 76 even when the claw portion 76protrudes beyond the slit hole 60 and clamps the workpieces W1, W2.

As a result, for example, it can be reliably prevented by the shutter 66for foreign matter such as spatters and the like which are produced inperforming the welding of the workpieces W1, W2 clamped by the clamp arm20 to enter the inside of the body 16 through the slit hole 60.

Further, by keeping the claw portion 76 of the clamp arm 20 alwaysinserted into the clamp hole 72 of the shutter 66, it is possible tomove the shutter 66 integrally with the vertical movement of the clamparm 20.

Furthermore, by providing between the cylinder section 14 and the body16 the lock switching mechanism 22 which is able to lock the operationof the clamp arm 20, it is possible for the lock switching mechanism 22to reliably and stably maintain the clamping state where the workpiecesW1, W2 are clamped by the clamp arm 20, even when the supply ofpressurized fluid to the cylinder section 14 is stopped.

Still furthermore, the lock ring 88 being part of the lock switchingmechanism 22 is provided with the release lever 96 operable from outsidethe housing 86. Thus, even in the case where the lock state of thepiston rod 28 by the lock ring 88 cannot be released because the supplyof pressurized fluid to the lock release port 92 of the housing 86stops, the worker can manually release the lock state by pressing therelease lever 96 down to forcibly tilt the lock ring 88.

Further, the shutter 66 is not limited to the cylindrical one having theconstant diameter as described above, and instead, there may be used,for example, any one of shutters (cover members) 120, 130, 140, 150, 160according to first to sixth modifications shown in FIGS. 7A to 7F.

First of all, as shown in FIG. 7A, a shutter 120 according to a firstmodification is formed of a metal material being elastically deformablein the radial direction and is formed in a C-shape in cross section bybeing cut out at a portion on a side opposite to a clamp hole 72. Acutout portion 122 is formed at a predetermined area along thecircumferential direction and extends in the axial direction (the arrowA-B direction). The shutter 120 is fitted in the chamber 64 of thelocating section 54 while pressed radially inward and reduced indiameter.

That is, in the shutter 120 according to the first modification, sincethe portion diametrically opposite to the clamp hole 72 is cut out, itis possible to improve insertability in inserting the other end portionof the clamp arm 20 inside the shutter 66 and to reduce an areacontacting with the clamp arm 20 by the provision of the cutout portion122. This makes it possible, for example, to increase the dimension ofthe clamp arm and to increase the degre of freedom in design.

In a shutter 130 according to a second modification, as shown in FIG.7B, there is provided a bellows portion 136 which connects a main bodyportion 132 having a clamp hole 72 to an upper end portion 134, and thebellows portion 136 is formed of, for example, an incombustible resinmaterial and is provided expansibly in the axial direction (the arrowA-B direction). Further, inside the bellows portion 136 a spring 138 isprovided urging the main body portion 132 and the upper end portion 134to separate from each other.

When the shutter 130 goes up together with the clamp arm 20 along thelocating section 54, the bellows portion 136 is compressed against theresilient force of the spring 138 upon abutment of the upper end portion134 on the upper end portion of the chamber 64, so that the length ofthe shutter 130 in the axial direction (the arrow A-B direction) isshortened.

On the other hand, when the shutter 130 goes down together with theclamp arm 20, the upper end portion 134 moves in the direction away fromthe locating section 54. As a result, the upper end portion 134 movesaway from the main body portion 132 because the bellows portion 136 isexpanded by the resilient force of the spring 138, so that the length ofthe shutter 130 in the axial direction is elongated to cover the slithole 60 with the bellows portion 136.

That is, in the shutter 130 according to the second modification,because of having the axially expansible bellows portion 136, thelongitudinal dimension of the shutter 130 can be shortened when theshutter 130 goes up. Therefore, it is possible to decrease the heightdimension of the locating section 54 housing the shutter 130 and hence,to downsize the height dimension of the clamping device 10.

Further, in place of the bellows portion 136 of the shutter 130 in theaforementioned second modification, there may be provided an expansibleportion 142 of a telescopic configuration which is expansible in theaxial direction like a shutter 140 according to a third modificationshown in FIG. 7C. Alternatively, there may be provided a covered portion152 which is made of a fabric being axially flexible like a shutter 150according to a fourth modification shown in FIG. 7D. Incidentally, theexpansible portion 142 and the covered portion 152 are respectivelyformed of incombustible resin and fabric.

Even in the shutters 140, 150 according to the third and fourthmodifications, it is possible to downsize the longitudinal dimension ofeach shutter 140, 150 when the shutters go up inside the locatingsection 54. Accordingly, it becomes possible to decrease the heightdimension of the locating section 54 housing the shutter 140 or 150 andhence, to downsize the height dimension of the clamping device 10.

In a shutter 160 according to a fifth modification, as shown in FIG. 7E,the shutter 160 includes a cylindrical outer sleeve 162 and an innersleeve 164 provided inside the outer sleeve 162. The outer sleeve 162 isformed with a first insertion groove 166 slanted at a predeterminedangle with respect to the axis, while the inner sleeve 164 is formedwith a second insertion groove 168 slanted at a predetermined angle withrespect to the axis and crossing the first insertion groove 166substantially perpendicularly.

Further, in the shutter 160, the first insertion groove 166 and thesecond insertion groove 168 intersect each other, and the claw portion76 of the clamp arm 20 is inserted into both the first and secondinsertion grooves 166, 168 at the intersection portion.

Thus, for example, when the clamp arm 20 is moved upward for example,the claw portion 76 is moved upward along the first and second insertiongrooves 166, 168 while the outer sleeve 162 and the inner sleeve 164 arecaused to respectively turn in opposite directions, so that the slithole 60 is covered by the outer sleeve 162 and the inner sleeve 164.

On the other hand, when the clamp arm 20 is moved downward, the clawportion 76 is moved along the first and second insertion grooves 166,168 toward respective lower ends thereof. Thus, the outer sleeve 162 andthe inner sleeve 164 are reversely turned in opposite directions, sothat the slit hole 60 is covered by the outer sleeve 162 and the innersleeve 164.

That is, in the shutter 160 according to the fifth modification, theouter sleeve 162 and the inner sleeve 164 only turn and are not moved inthe vertical direction (the arrow A-B direction). Accordingly, it ispossible to decrease the height dimension of the locating section 54housing the shutter 160 and hence, to downsize the height dimension ofthe clamping device 10.

Further, like a shutter 170 according to a sixth modification shown inFIG. 7F, an outer sleeve 172 and an inner sleeve 174 are formed in aC-shape in cross section by being each provided with a cutout portion176. With this configuration, in addition to an advantage attained bythe shutter 160 that the height dimension of the clamping device 10 isdownsized by decreasing the height dimension of the locating section 54,it is possible to improve the insertability when the other end portionof the clamp arm 20 is inserted inside the inner sleeve 174 and toenhance the degree of freedom in designing the clamp arm 20.

Obviously, the present invention is not limited to the foregoingembodiment and modifications. It is of course possible that the presentinvention may take various configurations without departing from thegist of the present invention.

1. A clamping device comprising: a drive section having a displacementbody movable in an axial direction under an action of supplyingpressurized fluid; a body connected to the drive section and having amounting portion on which a workpiece is mounted; a clamp arm connectedto the displacement body and pivotably supported relative to the body; alocating section protruding in the axial direction relative to themounting portion and being inserted into a positioning hole formed inthe workpiece; wherein a linear motion of the displacement bodyoutputted by the drive section is converted into a pivotal motion of theclamp arm, a slit hole is formed in the locating section and opens alongthe axial direction, a claw portion of the clamp arm housed inside thelocating section protrudes through the slit hole, the workpiece isclamped between the mounting portion and the claw portion, a covermember that faces the slit hole and is movable in the axial direction isprovided inside the locating section; and the cover member is providedwith an opening into which the claw portion is inserted, the openingfaces the slit hole.
 2. The clamping device according to claim 1,further comprising: a lock mechanism configured to restrict the pivotalmotion of the clamp arm.
 3. The clamping device according to claim 2,wherein: the lock mechanism includes a lock member that is tiltable withrespect to the axial direction of the displacement body and restricts amovement of the displacement body when the lock member is tilted.
 4. Theclamping device according to claim 3, wherein: the lock member tilts apredetermined angle urged by a resilient member; and when thepressurized fluid is supplied, the lock member returns from a statewhere the member tilts to a state where the displacement body ismovable.
 5. The clamping device according to claim 1, wherein: the covermember is formed in a C-shape in cross section and extends in the axialdirection.
 6. The clamping device according to claim 1, wherein: thecover member is formed to be expansible in the axial direction in whichthe cover member is moved.